View Full Version : Measuring amplitude

06-09-2005, 10:13 PM
I want to monitor a DC signal and when its amplitude gets over X, then the STAMP will output a high signal to a pin. I will set X using a turn-pot. I am not too sure what approach to take concerning the amplitude measurement. Any ideas? Thanks in advance

06-09-2005, 10:53 PM
After writing the post, maybe amplitude isn't the correct term. Variance over time might be better, amplitude implies a sine wave type of DC input.

Tom Walker
06-09-2005, 11:02 PM
If you're talking about a voltage exceeding a certain value, this is typically the job for a comparitor. But I'm not certain that this is what you are trying to determine. A more complete description of your requirements would help get a more complete solution.

Truly Understand the Fundamentals and the Path will be so much easier...

06-09-2005, 11:17 PM
The input voltage is from a 6'' linear pot that measures shock position on a race car. Normally, the shocks don't move much at all. However there are certain situations where the shock will compress and while it is compressing, the shock is oscillating. The data looks like a sine wave tilted at about a 20 degree from horizontal angle. I want to detect this event with a STAMP and output a 5v signal to trigger another device on the car.

Attached is a screen shot of data. The red trace is shock position from the linear pot. The area inside the yellow box is what I want to detect.

Post Edited (TG) : 6/9/2005 4:36:24 PM GMT

06-10-2005, 12:19 AM
without additional circuitry you could just read the POT position in to the stamp....RCTime is a way to measure analog devices or you could use an Analog to Digital converter.

IF the pulses transitioned the 2.4V logic threshold (hope I got that level right) then you could use the count command or pulsin (being that it's about a 24Hz ringing).

http://cache.national.com/ds/LM/LM231.pdf this is a voltage to freq converter but they do have a sample circuit for a freq to voltage converter....of course you might need to amplify your ringing so that it crosses a certain voltage level!


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06-10-2005, 02:27 AM
Being a race car application, I suspect you want to recognize this event and act as soon as possible? The Stamp may not be a wise choice to act quickly, but that all depends upon your definition of quick. Do you know the maximum time delay you can allow for the event to be recognized and acted upon?

LM2907....and look at the Typical Applications section. If you have questions on its operation, write back.


Post Edited (KenM) : 6/9/2005 7:31:58 PM GMT